Low Environmental Concentrations Research Articles

Effects of nanoplastics at predicted environmental concentration on Daphnia pulex after exposure through multiple generations

The biological effects of nanoplastics are a growing concern. However, most studies have focused on exposure to high concentrations or short-term exposure. The potential effects of exposure to low environmental nanoplastic concentrations over the long-term and across multiple generations remain unclear. In the present study, Daphnia pulex was exposed over three 21-day generations to a typical environmental nanoplastic concentration (1 μg/L) and the effects were investigated at physiological (growth and reproduction), gene transcription and enzyme activity levels. Chronic exposure did not affect the survival or body length of D. pulex, whereas the growth rate and reproduction were influenced in the F2 generation. Molecular responses indicated that environmental nanoplastic concentrations can modulate the response of antioxidant defenses, vitellogenin synthesis, development, and energy production in the F0-F1 generations, and prolongation resulted in inhibitory effects on antioxidant responses in F2 individuals. Some recovery was observed in the recovery group, but reproduction and stress defenses were significantly induced. Taken together, these results suggest that D. pulex recovery from chronic exposure to nanoplastic may take several generations, and that nanoplastics have potent long-term toxic effects on D. pulex. The findings highlight the importance of multigenerational and chronic biological evaluations to assess risks of emerging pollution.

Combined study of source, environmental monitoring and fate of branched alkylphenols: The chain length matters.

Alkylphenols (APs) are chemicals of largely anthropogenic origin. Longer chain derivatives like 4-nonylphenol (4NP) or 4-tert.-octylphenol (4tOP) are mainly used for the production of alkylphenol ethoxylates, while short chain alkylphenols (SCAPs) can be applied during the production of phenolic or epoxide resins that are used in paint, glue or adhesive formulations. The source, environmental distribution and fate of 4NP and 4tOP were thoroughly demonstrated leading to growing concerns regarding their endocrine properties. Although, SCAPs are also expected to entail risks to the aquatic environment, only few studies dealt with the identification of possible sources or environmental concentrations thereof.In order to evaluate the role of resin-based building materials as a possible source of 4-tert.-butylphenol (4tBP), 4-tert.-pentylphenol (4tPP), 4tOP and 4NP, 18 formulations were tested. Furthermore, AP concentrations of four wastewater treatment plants (WWTPs) and 50 surface waters were analyzed to assess and compare environmental concentrations and the discharge of APs depending on their chain length. 4tBP was the dominant AP in analyzed building materials with concentrations up to 320 g kg−1. Furthermore, APs were detected in all WWTPs and waterbodies. 4NP was the dominant AP in most surface water and WWTP samples ranging from <LOQ-0.5 μg L−1 and <LOQ-2.34 μg L−1, respectively, whereas 4tPP was rarely detected over all samples. Observed detection patterns of 4tBP in surface waters indicated different entrance pathways and hence, different sources compared to 4NP and 4tOP. Furthermore, WWTP samples and accompanying transformation studies pointed towards rapid biotransformation of 4tBP, explaining low environmental concentrations.

Analysis of polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives in soils of an industrial heritage city of Australia

Knowledge about polar derivatives of polycyclic aromatic hydrocarbons (PAHs) in soils is limited despite the extensive study of the environmental presence and persistence of non-polar parent PAHs. Polar PAHs have greater potential to be more toxic at low environmental concentrations compared to their homocyclic analogues. For both polar and non-polar PAHs, combustion of fossil fuels is often the main source especially in industrialised environments. This study investigated the concentration profiles of PAHs and its associated polar PAHs such as nitrated PAHs (NPAHs), oxygenated PAHs (oxy-PAHs) and nitrogen, sulphur and oxygen heterocyclic PAHs (N/S/O-heterocyclic PAHs) in a well-known industrial heritage city of Australia. The most abundant polar PAHs were 9-fluorenone (oxy-PAHs), 2-nitrofluorene (NPAHs) and carbazole (heterocyclic-PAHs). A positive correlation (r = 0.5, p < 0.01) between ∑13PAHs and ∑19 polar PAHs was observed, implying a possible spatial association between parent and polar PAHs. The concentrations of polar PAHs in soil samples, across various landuse patterns, were used to calculate the excess lifetime cancer risk (ELCR) from incidental ingestion of soils. The computed ELCR values ranged from 8.2*10−7 (industrial soils) to 2.3*10−6 (residential soils), indicating negligible cancer risks. This is the first known study on the occurrence and concentrations of polar and non-polar PAHs in any Australian city, and the results may serve a baseline purpose for improved risk assessment of contaminated sites.

Compositional alterations in soil bacterial communities exposed to TiO2 nanoparticles are not reflected in functional impacts

Titanium dioxide nanoparticles (TiO2NP) are increasingly released in soil ecosystems, while there is limited understanding of the impacts of TiO2NP on soil bacterial communities. Here we investigated the effects of TiO2NP on the taxonomic composition and functional profile of a soil bacterial community over a 60-day exposure period. In short-term exposure (1-day), contradictory effects on the taxonomic composition of soil bacterial communities were found after exposure to a low realistic environmental concentration of TiO2NP at 1 mg/kg as compared to the effects induced by medium and high concentrations of TiO2NP at 500 and 2000 mg/kg. After long-term exposure (60-day), the negative effects of TiO2NP at the low concentration disappeared, and the inhibition by TiO2NP of the abundance of core taxa was enhanced along with increasing exposure concentrations. However, although significant alterations were observed in the taxonomic composition over time and exposure concentrations, no significant change was observed in the community functional profile as well as enzyme activity after 60-day exposure, indicating that functional redundancy likely contributed to the bacterial community tolerance after the exposure to TiO2NP. Our study highlighted the importance of assessing bacterial community compositional and functional responses in assessing the environmental risk of nanoparticles on soil ecosystems.

Sunscreens as a New Source of Metals and Nutrients to Coastal Waters.

Studies detailing the environmental impact of sunscreen products on coastal ecosystems are considered a high priority. In the present study, we have determined the release rate of dissolved trace metals (Al, Cd, Cu, Co, Mn, Mo, Ni, Pb, and Ti) and inorganic nutrients (SiO2, P-PO43-, and N-NO3-) from a commercial sunscreen in seawater, and the role of UV radiation in the mobilization of these compounds. Our results indicate that release rates are higher under UV light conditions for all compounds and trace metals except Pb. We have developed a kinetic model to establish the release pattern and the contribution to marine coastal waters of dissolved trace metals and inorganic nutrients from sunscreen products. We conservatively estimate that sunscreen from bathers is responsible for an increase of dissolved metals and nutrients ranging from 7.54 × 10-4 % for Ni up to 19.8% for Ti. Our results demonstrate that sunscreen products are a significant source of metals and inorganic nutrients to coastal waters. The normally low environmental concentrations of some elements (e.g., P) and the toxicity of others (e.g., Pb) could be having a serious adverse effect on marine ecology in the Mediterranean Sea. This risk must not be ignored.

Application of the apatite oxygen paleobarometer (AOP) across the Neoproterozoic-Cambrian transition

Fluorescence signatures of samarium3+ substituted into apatite for calcium2+ have been shown experimentally to correlate with oxygen availability, such substituted apatite being a principal diagenetic mineral emplaced in shallow-water environments during the Neoproterozoic-Cambrian global phosphogenic event coeval with the “Cambrian Explosion of Life.” The occurrence of Sm3+-substituted apatite, encrusting, infilling and permineralizing components of shallow water microbial communities suggested that quantification of these fluorescence signatures might provide a widely applicable mineral-based paleobarometer by which to measure oxygen concentrations in the environment in which such apatite precipitated. To test this hypothesis, fluorescence spectroscopic analyses have been carried out on the Sm3+-substituted apatite of photic-zone microscopic fossils and fossil-associated ooids of near-shore facies of the Ediacaran Doushantuo (South China) and Early Cambrian Chulaktau (South Kazakhstan) Formations, and of the open ocean apatite-biomineralized phytoplanktonic “scale fossils” (Characodictyon) of the mid-Neoproterozoic (Tonian) Fifteenmile Group (Yukon Canada). Results obtained – quantified by the newly devised apatite oxygen paleobarometer metric – indicate a low (<5% O2) oxygen concentration in the depositional environment of the Ediacaran Doushantuo, a similarly low but slightly higher O2 level in the Early Cambrian Chulaktau, and are consistent with a low oxygen concentration in the scale fossil-evidenced mid-Neoproterozoic photic zone of the open marine environment. By documenting the rise of oxygen across the Neoproterozoic-Cambrian transition these results confirm the efficacy of this newly devised technique and suggest its value for future global application.

Environmentally relevant concentrations of methamphetamine and sertraline modify the behavior and life history traits of an aquatic invertebrate

Pharmaceutically active compounds are major contaminants of aquatic environments that show direct and indirect effects on aquatic organisms even at low concentrations. The aim of this study was to assess the effects of the illicit drug methamphetamine and the antidepressant sertraline on clonal marbled crayfish Procambarus virginalis. Crayfish exposed to the environmentally relevant concentrations of methamphetamine of ∼1 μg L−1 did not exhibit significant differences from unexposed controls in distance moved, velocity, and activity level with or without available shelter. Sertraline-exposed (∼1 μg L−1) crayfish were significantly more active, regardless of available shelter, and moved greater distances when shelter was available, compared to control crayfish. Crayfish exposed to methamphetamine and sertraline spent significantly more time outside the shelters compared to controls. Sertraline-exposed crayfish spawned more frequently and showed higher mortality than controls. The results suggest that the low environmental concentrations of the tested compounds could alter the behavior and life history traits of crayfish, resulting in higher reproductive effort and mortality.

Identification and functional analysis of the Mandarin fish (Siniperca chuatsi) hypoxia-inducible factor-1α involved in the immune response

Mandarin fish (Siniperca chuatsi) is a popular cultured freshwater fish species due to its high market value in China. With increasing density of breeding, mandarin fish is often cultured under low environmental oxygen concentrations (hypoxia). In this study, the relative expression levels of hypoxia response element (HRE)-luciferase reporter and the HIF signaling pathway downstream genes (scldha, scvegf, and scglut-1) were significantly increased by hypoxic stress, thereby indicating that mandarin fish has an HIF signaling pathway. The mandarin fish HIF-1α (scHIF-1α) was also characterized. Multiple sequence alignments showed that scHIF-1α presented similar architectures to other known vertebrates. Subcellular localization analysis showed that scHIF-1α was mainly located in the nucleus of the mandarin fish fry-1 (MFF-1) cells. The role of scHIF-1α in the regulation of the HIF signaling pathway was confirmed. Overexpression of scHIF-1α could induce the HIF signaling pathway, whereas knockdown of scHIF-1α inhibited the activity of the HIF-1 signaling pathway. Tissue distribution analysis showed that schif-1α was significantly highly expressed in the blood, heart, and liver, which indicated that the main function of scHIF-1α was closely related to the circulatory system. Furthermore, scHIF-1α expression was significantly induced by poly I:C, poly dG:dC or PMA, thereby indicating that scHIF-1α was involved in the immune response. HIF-1α plays an important role in pathogen infections in mammals, but its role in fish is rarely investigated. Overexpression of scHIF-1α could inhibit MRV and SCRV infections, whereas knockdown of scHIF-1α could promote such infections. Those results suggested that scHIF-1α played an important role in fish virus infection. Our study will help understand the hypoxia associated with the outbreaks of aquatic viral disease.

Bioaerosol biomonitoring: Sampling optimization for molecular microbial ecology.

Bioaerosols (or biogenic aerosols) have largely been overlooked by molecular ecologists. However, this is rapidly changing as bioaerosols play key roles in public health, environmental chemistry and the dispersal ecology of microbes. Due to the low environmental concentrations of bioaerosols, collecting sufficient biomass for molecular methods is challenging. Currently, no standardized methods for bioaerosol collection for molecular ecology research exist. Each study requires a process of optimization, which greatly slows the advance of bioaerosol science. Here, we evaluated air filtration and liquid impingement for bioaerosol sampling across a range of environmental conditions. We also investigated the effect of sampling matrices, sample concentration strategies and sampling duration on DNA yield. Air filtration using polycarbonate filters gave the highest recovery, but due to the faster sampling rates possible with impingement, we recommend this method for fine ‐scale temporal/spatial ecological studies. To prevent bias for the recovery of Gram‐positive bacteria, we found that the matrix for impingement should be phosphate‐buffered saline. The optimal method for bioaerosol concentration from the liquid matrix was centrifugation. However, we also present a method using syringe filters for rapid in‐field recovery of bioaerosols from impingement samples, without compromising microbial diversity for high ‐throughput sequencing approaches. Finally, we provide a resource that enables molecular ecologists to select the most appropriate sampling strategy for their specific research question.

Using an apex predator for large-scale monitoring of trace element contamination: Associations with environmental, anthropogenic and dietary proxies

Understanding the levels and drivers of contamination in top predators is important for their conservation and eventual use as sentinels in environmental monitoring. Therefore, metals and trace elements were analyzed in feathers of Bonelli's eagles (Aquila fasciata) from southern Portugal in 2007–2013, where they are believed to be exposed to a wide range of contamination sources such as agricultural land uses, urban areas, active and abandoned mines and a coal-fired power plant. We focused on concentrations of aluminum (Al), arsenic (As), copper (Cu), chromium (Cr), mercury (Hg), lead (Pb), selenium (Se) and zinc (Zn), as these contaminants are potentially associated with those sources and are known to pose a risk for terrestrial vertebrates. Stable isotope values of nitrogen (δ15N: 15N/14N), carbon (δ13C: 13C/12C) and sulphur (δ34S: 34S/32S) were used as dietary proxies to control for potential effects of prey composition on the contamination pattern. The spatial distribution of potential contamination sources was quantified using geographic information systems. Concentrations of Hg in the southern part of the study area were above a reported toxicity threshold for raptors, particularly in territories closer to a coal-fired power plant at Sines, showing that contamination persisted after a previous assessment conducted in the 1990s. Hg and Se levels were positively correlated with δ15N, which indicates biomagnification. Concentrations of As, Cr, Cu, Pb and Zn were generally low and unrelated to mining- or industrial activities, indicating low environmental background concentrations. Al was found at higher concentrations in the southernmost areas of Portugal, but this pattern might be related to external soil contamination on feathers. Overall, this study indicates that, among all elements studied, Hg seems to be the most important contaminant for Bonelli's eagles in southern Portugal, likely due to the power plant emissions and biomagnification of Hg in terrestrial food webs.

Removal of La(III) ions from aqueous solution by Lanthanide MOF; characterization, synthesizing and process conditions study

Providing fresh water resources for humans is highly attended in regard to environmental and human health protection. Lanthanum (La), as one of the common water contaminations, has been eliminated using various methods. However, its removal from water is very challenging due to its low concentration in the aquatic environment. In this study, microporous Ce-BTC MOF has been employed for puissant removal of La ions under multiple synthesizing and experimental conditions. The as-synthesized Ce-BTC MOF was characterized by the assist of FTIR, XRD, SEM, and TGA characterization analyses. It has been deduced that reactor volume, type of surfactant, filtration solvent, and degassing temperature have a significant role on the pore structure of final prepared Ce-BTC MOF. The adsorption process was examined for adsorption time, adsorbent dose, initial concentrations, and temperatures. For prediction of the process behavior, different models were used to describe isotherm and mechanism of the adsorption process. Fabricated MOF removed more than 75% of La ions in 60 min on adsorbent loading of 2 mg/L. Accordingly, it is expected for this synthesized adsorbent to have promising potential for removal of La ions at optimum conditions.

Synthesis and low-temperature sensing property of the porous ZnCo2O4 nanosheets

Hydrogen sulfide even with low concentration in environment is very pernicious to the health, Therefore, the design of gas sensors for detecting H2S is highly desirable. In this work, porous spinel ZnCo2O4 nanosheets (NSs) were synthesized via a hydrothermal method and followed by the thermal treatment. Structural characterizations indicate that the porous NSs are composed of ~ 14 nm interconnected ZnCo2O4 nanoparticles. The porous spinel ZnCo2O4 NSs exhibit enhanced H2S sensing performance in comparison to Co3O4 NSs. The detection limit of the porous ZnCo2O4 NSs is down to 100 ppb H2S with a sensor response value of 1.32 even at relatively low operating temperature of 120 °C. Furthermore, the porous ZnCo2O4 NSs have fascinating selectivity and good long-term stability and relatively rapid response time. The gas sensing mechanism of the ZnCo2O4 NSs gas sensor is also discussed in terms of the effects of oxygen vacancies. In view of the exciting gas-sensing properties and facile preparation method, the porous ZnCo2O4 NSs are ideal candidates for the H2S sensors.

Citric acid cross-linking of highly porous carboxymethyl cellulose/poly(ethylene oxide) composite hydrogel films for controlled release applications

Herein, highly porous hydrogel made up from citric acid cross-linking of carboxymethyl cellulose (CMC) composite with poly(ethylene oxide) (PEO). The swelling behavior of CMC/PEO hydrogel was evaluated based on four parameters; ratio of CMC to PEO, percentage of citric acid, temperature and duration of curing. The optimum degree of swelling was found to be at 3:1 ratio of CMC/PEO, 10% of citric acid, 70°C of curing temperature and 450 minutes of curing time. Degree of swelling and thermal stability of the hydrogel film improved when CMC was composited with PEO compared to CMC alone. Gel fraction of CMC/PEO hydrogel film was 44.17% with high loading percentage of 82.69 ± 0.58% of methylene blue (MB). The MB released from CMC/PEO hydrogel was pH dependent, where MB was released with low concentration in acidic environment compared to basic environment. The results show CMC/PEO hydrogel have high potential to be used in controlled drug release for biomedical applications.

Solid-phase extraction method for stable isotope analysis of pesticides from large volume environmental water samples.

Compound-specific isotope analysis (CSIA) is a valuable tool for assessing the fate of organic pollutants in the environment. However, the requirement of sufficient analyte mass for precise isotope ratio mass spectrometry combined with prevailing low environmental concentrations currently limits comprehensive applications to many micropollutants. Here, we evaluate the upscaling of solid-phase extraction (SPE) approaches for routine CSIA of herbicides. To cover a wide range of polarity, a SPE method with two sorbents (a hydrophobic hypercrosslinked sorbent and a hydrophilic sorbent) was developed. Extraction conditions, including the nature and volume of the elution solvent, the amount of sorbent and the solution pH, were optimized. Extractions of up to 10 L of agricultural drainage water (corresponding to up to 200 000-fold pre-concentration) were successfully performed for precise and sensitive carbon and nitrogen CSIA of the target herbicides atrazine, acetochlor, metolachlor and chloridazon, and metabolites desethylatrazine, desphenylchloridazon and 2,6-dichlorobenzamide in the sub-μg L-1-range. 13C/12C and 15N/14N ratios were measured by gas chromatography-isotope ratio mass spectrometry (GC/IRMS), except for desphenylchloridazon, for which liquid chromatography (LC/IRMS) and derivatization-GC/IRMS were used, respectively. The method validated in this study is an important step towards analyzing isotope ratios of pesticide mixtures in aquatic systems and holds great potential for multi-element CSIA applications to trace pesticide degradation in complex environments.

Minor environmental concentrations of antibiotics can modify bacterial virulence in co-infection with a non-targeted parasite.

Leakage of medical residues into the environment can significantly impact natural communities. For example, antibiotic contamination from agriculture and aquaculture can directly influence targeted pathogens, but also other non-targeted taxa of commensals and parasites that regularly co-occur and co-infect the same host. Consequently, antibiotics could significantly alter interspecific interactions and epidemiology of the co-infecting parasite community. We studied how minor environmental concentrations of antibiotic affects the co-infection of two parasites, the bacterium Flavobacterium columnare and the fluke Diplostomum pseudospathaceum, in their fish host. We found that antibiotic in feed, and particularly the minute concentration in water, significantly decreased bacterial virulence and changed the infection success of the flukes. These effects depended on the level of antibiotic resistance of the bacterial strains. Antibiotic, however, did not compensate for the higher virulence of co-infections. Our results demonstrate that even very low environmental concentrations of antibiotic can influence ecology and epidemiology of diseases in co-infection with non-targeted parasites. Leakage of antibiotics into the environment may thus have more complex effects on disease ecology than previously anticipated.

Changes in the gills of the European eel (Anguilla anguilla) after chronic exposure to environmental cocaine concentration

The recent discovery of illicit drugs in the aquatic environment has raised concerns about the possible effects on the aquatic fauna, because of the pharmacological activity of these substances. Cocaine is an illicit drug widespread in surface waters since it is the third most widely used drug in North America, Western and Central Europe, and the second in Latin America and the Caribbean. The aim of this study was to evaluate the influence of environmental concentrations of cocaine on the gills of the European eel (Anguilla anguilla). The gills of male silver eels exposed to 20 ng L−1 of cocaine for fifty days were compared to control, vehicle control and post-exposure recovery ten days groups. The following parameters were evaluated: the thickness of the interlamellar epithelium (TIE), the length of the secondary lamellae (LSL) and the fraction of the interlamellar epithelium and the secondary lamellae occupied by the mucous cells (MC(IE-SL)FA) 3) the plasma cortisol and prolactin levels. After cocaine exposure, the gill epithelium appeared hyperplastic. The following changes were observed: proliferation in the interlamellar epithelium; partial and total fusion of the secondary lamellae, that appeared shortened and dilated; epithelial lifting and aneurism in the secondary lamellae. Moreover, in cocaine exposed eels, an increase in TIE and MC(IE-SL)FA and a decrease in LSL were observed. These changes were still present ten days after the interruption of cocaine exposure. Plasma levels of both cortisol and prolactin increased after cocaine exposure; ten days after the interruption of cocaine exposure, the plasma cortisol levels were still higher, whereas the plasma prolactin levels were lower, than control values. Our results show that even a chronic exposure to low environmental cocaine concentrations severely harms the eel gills, suggesting damages to their functions, and potentially affecting the survival of this species.

ONE HEALTH: ENVIRONMENTAL CONTAMINATION BY ANTIMICROBIALS

Over the past few decades, a high number of pharmaceuticals have been detected in surface, ground and drinking waters. This contamination comes from domestic sewage, livestock, hospitals and chemical- pharmaceutical industries. Typical examples of these pollutants are the antimicrobials – powerful antibiotics used in human and veterinary medicine. The presence of antimicrobials in the environment can pose a serious threat to the ecosystem and to human health due to their high consumption globally. Even at low environmental concentrations, antibiotics stimulate bacterial resistance. The consequences of the presence of fluoroquinolones in the environment are not fully understood, but are known to be toxic to plants and aquatic organisms. Approximately 85% of the antimicrobials present in influents can be removed by conventional wastewater treatment plants, but the removed fraction is frequently accumulated in the sludge, which is sometimes used as fertilizer, representing an additional input route into the environment. The removal of antimicrobials by biological treatment is ineffective, and it is believed that only advanced oxidation technologies are able to destroy these emerging pollutants.

Exploitation of a photoelectrochemical sensing platform for bisphenol A quantitative determination using Cu/graphitic carbon nitride nanocomposites

A simple and effective photoelectrochemical sensor was fabricated by Cu/graphitic carbon nitride (Cu/g-CN) composites for detecting bisphenol A. The Cu/g-CN composites were obtained via a solvothermal process in the presence of the copper-based ionic liquid. In view of localized surface plasmon resonance of Cu nanoparticles, Cu nanoparticles can promote light absorbance and rapid electron transport of g-CN. As a result, the Cu/g-CN composites obtained greatly enhancement of photocurrent, when compared to the pure g-CN. In addition, the introduction of bisphenol A can hinder electron-hole recombination, resulting in sensitive photoelectrochemical monitoring of bisphenol A. The detection limit of the bisphenol A photoelectrochemical sensor was below 0.012 μmol/L. The bisphenol A photoelectrochemical sensor exhibited an excellent stability and acceptable anti-interference. The photoelectrochemical sensor provided the promising platform to monitor bisphenol A at low concentration in water environment.

Endocrine disruption in Chinese rare minnow (Gobiocypris rarus) after long-term exposure to low environmental concentrations of progestin megestrol acetate

Synthetic progestins are widely used pharmaceutical agents that have become common contaminants in the aquatic environment. The potential adverse effects of long-term exposure on aquatic wildlife, however, are not fully understood. The aim of this study was to investigate the endocrine disruption in Chinese rare minnow (Gobiocypris rarus) in response to megestrol acetate (MTA) exposure. Newly-hatched Chinese rare minnow larvae were exposed to MTA at a nominal concentration of either 1 ng/L (detected concentrations ranged from 0.18 to 0.93 ng/L) or 10 ng/L (detected concentrations ranged from 4.27 to 9.64 ng/L) for 6 months and the effects on growth, sex steroid hormones, gonadal histology, and steroidogenic genes expression were determined. After 6 months of exposure to a nominal concentration of 10 ng/L MTA, the body weight and condition factors were significantly increased in fish of both sexes. Exposure to a nominal concentration of 10 ng/L MTA significantly reduced plasma concentrations of estradiol and 11-ketotestosterone in female fish while also reducing testosterone and 11-ketotestosterone in male fish. Gonad histology revealed significantly reduced proportions of vitellogenic oocytes in female fish exposed to a nominal concentration of 10 ng/L MTA and induction of atretic follicles in female fish exposed to both nominal concentrations of MTA. The expression of cyp19a1a and cyp17a1 in the gonads was up-regulated in the ovaries while down-regulated in the testes. Our results indicate that MTA can induce endocrine disruption in Chinese rare minnow at the low concentrations found in contaminated environments. This indicates a potentially high ecological risk from MTA to fish populations in MTA-contaminated aquatic environments in China and may also in other regions.

Long term exposure to environmental concentrations of diesel exhaust particles does not impact the phenotype of human bronchial epithelial cells

Chronic exposure to diesel engine exhausts is associated with an increased risk of pulmonary diseases including lung cancer. Diesel engine exhausts contain large amounts of diesel exhaust particles (DEP) on which are adsorbed several carcinogenic compounds such as polycyclic aromatic hydrocarbons. Acute toxicity of high concentrations of DEP has been largely demonstrated in various in vitro cellular models. In contrast, the cellular and molecular impacts of low environmental concentrations of DEP on the phenotype of chronically exposed lung epithelial cells remain to be investigated. In the present study, we show that long term exposure (6 months) to 2 μg/ml (0.4 μg/cm2) DEP (standard reference material 1650b) increased cytochrome P4501A mRNA levels in the human bronchial epithelial BEAS-2B cell line. However, chronic exposure to DEP did not change cell morphology, trigger epithelial-mesenchymal transition or increase anchorage-independent cell growth. Moreover, DEP increase neither the levels of reactive oxygen species or those of γ-histone H2AX, nor the expression of interleukin-6 and interleukin-8. Our results thus demonstrate that the chronic exposure to low DEP concentrations could increase cytochrome P501A gene expression in BEAS-2B cells but did not induce molecular effects related to genotoxicity, oxidative stress or inflammation.